Richard Jackson BVMS (Hons) MRCVS
The very mention of the words Avian Influenza (AI) or bird flu strikes fear into the hearts of poultry keepers and the general public alike.
Avian Influenza is caused by an Influenza virus, of which there are several strains. Some of these strains infect only people, whilst others infect only birds. Some strains have the ability to infect more than one species; however in these cases, the virus tends to have a preference for infecting one species, e.g. A strain of Influenza that infects birds may readily spread between poultry but may struggle to infect people and will only do so in rare circumstances. Why human health professionals become concerned about bird flu is that if there ever was a strain that could infect both people and birds readily, it would be a challenge to control.
Not only do different strains vary in terms of which species they prefer to infect, they also differ in the levels of harm they do to infected birds. As such, AI is split into two groups: High Pathogenic AI (highly harmful) and Low Pathogenic AI (less harmful). Unfortunately, as with all things in nature, AI does not fit nicely in to boxes and all strains lie on a sliding scale, whereby at one end, the viral strain is so harmful that affected birds are often found dead; through to relatively harmless strains whereby infected birds show mild sneezing. Only the Government Veterinary Laboratories Agency (VLA) can determine whether or not a given strain is classed as high or low pathogenic.
The virus is often carried and spread by waterfowl that are remarkably resistant to disease and rarely show clinical signs. As waterfowl often migrate large distances globally, AI can move between countries readily. Furthermore, both people and contaminated objects can carry the virus long distances.
Affected birds shed the virus in both their droppings and nasal discharge. Subsequently, other birds and perhaps mammals can pick the virus up by either inhaling or ingesting it. Once infected, birds can show clinical signs in as little as 24 hours.
Clinical signs include sudden death, respiratory distress, swollen face, sneezing (snicking), runny nose, runny eyes and nervous signs. Unfortunately, none of these signs are specific.
Due to the symptoms being rather non-specific, any suspicion of AI must be notified to your local Animal Health Office. From a backyard flock point of view, either the sudden and unexplained death of more than one bird, or illness in the entire flock, should be considered as a cause for concern and at least reported to your own vet to discuss.
Diagnosis can only be made by a vet taking blood samples or swabs.
When AI is suspected, Animal Health (a government agency) must be informed since Avian Influenza is a notifiable disease. They will visit the farm and take samples. If your birds are positive for the virus then sadly they would have to be put to sleep. Animal Health would look at birds on surrounding holdings to check for disease and take samples. Local poultry keepers will also likely be advised to keep all poultry indoors.
In these circumstances, it is very tempting keep your head down, say nothing and pretend that everything is okay. However, not notifying Animal Health or DEFRA of suspected cases could allow for the spread of the disease across the country, potentially leading to the deaths of millions of birds and in extreme circumstances you may be putting yourself and your family at risk.
Animal Health/DEFRA would use the GB Poultry Register to determine which holdings are near to a suspected outbreak. All poultry keepers with more than 50 birds are required to register. Those with less than 50 birds are advised to do so but it is not compulsory. Registration is free. We recommend that all poultry keepers register. Information can be found on the DEFRA website.
Prevention of AI in your flock involves keeping wild birds away. Trees in ranges look nice; provide shelter and shade as well as encouraging ranging. However, trees attract wild birds which can defecate on the range below possibly spreading AI. Feeding birds outside also attracts wild birds. Keepers of waterfowl should especially try to discourage wild birds from swimming in their ponds.
Whilst AI is easily spread, it is not resistant to disinfectants. It is important to prevent contact between wild birds and poultry in smallholdings, we advise housing the birds or using netting to cover areas to prevent wild birds accessing your birds’ food and water.
Many people ask about vaccination. However, whilst there are vaccines available globally, there are several strains of AI and therefore, it is almost impossible to have one for every strain out there. To make matters worse, AI is constantly changing meaning that a given vaccine may be useless within weeks or months of being manufactured. There is also an argument out there stating that vaccinated birds may become infected with AI but not show signs thus they would not be identified and spread the disease further.
Globally, AI is a problem mostly in the developing world rather than in the western world. Whilst DEFRA and Animal Health do their best to keep the disease out (including annual random routine testing), it is always possible that with migrating birds the disease may make its way into the UK. Poultry keepers are always advised to keep a look out for sudden death or severe respiratory signs in several birds in their flock. If you suspect AI, please contact DEFRA or Animal Health immediately.